Laboratory Centrifuge and Its Applications

Alexander Prandtl developed the first centrifugein 1875 for the separation of cream from milk. Since then, laboratory centrifuge  has becomeone of the critical tools in various scientific and clinical applications.

What is Centrifugation?

Centrifugation is atechnique to separate particles from a solution by the application of centrifugal forces and the separation is achieved based upon theparticle size, shape, density, viscosity of the solution, and centrifugal rotor speed.

Figure-1: Sample solution before and after centrifugation.

The concept of Centrifugation:

The centrifuge uses the process of centrifugation and the principle of centrifugal force. When an object is subjected to rotation around an axis, an outward radial force is applied to it. This centripetal force is used to accelerate sedimentation, a process where denser particles are thrown faster to the outward direction. The centrifugal principle is used for various applications in the modern labs, to separate various constitutes within the sample.

Figure-2:Principle of centrifugal force

What Types of Centrifuge are Available?

There are many types available in the market today; those are widely ranged with different rotor speed, refrigeration conditions, and centrifuge size. This article focuses mainly on laboratory centrifuges.

A laboratory centrifuge is driven by an electric motor, which rotates liquid suspensions at high speed. Centrifugal force causes the heavier particles to move to the outer part of the sample tube, and lighter particles move closer to the centre. Laboratory centrifuges work by the sedimentation principle, where the centripetal speed is used to separate the heavier and lesser density substances. When a sample in a centrifuge tube is centrifuged, the solids move to the bottom of the centrifuge tube. The shape of the centrifuge tube helps to takeout the solids easily

Figure-3: Centrifuge tube holder

Microcentrifuges generally work with small sample sizes of 0.2-10.0 ml, but some centrifuges have the Eppendorf placing capacity.A microcentrifuge allows to replace different capacity Eppendorf tubes, this gives greater flexibility in terms of sample capacity.

Figure-4: Mini Centrifuge

A benchtop centrifuge would be more beneficial for small laboratory applications; it also occupies less space. However, they only hold a small amount of material, so they are best used for applications where the sample size is small. Benchtop centrifuges may also come with a built-in refrigerator, but not all models contain it. If the sample undergoes the thermal degradation, it is advised to procure a refrigerated centrifuge. In general, benchtop centrifuges can be used for a variety of applications, including the samples containing blood, DNA, RNA, protein research, tissue culturing, and cell culturing.

Figure-5: Benchtop centrifuge

The regular centrifuges are used for the same functions as laboratory centrifuges, but regular centrifuges are larger than the laboratory and also called as floor model centrifuges. These types of centrifuges need more space than benchtop centrifuges, but they can manage a bigger sample size, and centrifuge tubes can hold up to 750 ml. The floor centrifuges may have the refrigeration function, and temperatures can be set between -20 °C and + 40 °C. The floor centrifuges are useful when the samples containing DNA, RNA, antibodies, viruses, or proteins.

The high capacity centrifuges are the ultracentrifuges in terms of acceleration, with a Relative Centrifugal Force of up to 1,000,000 g (150,000 RPM). The ultracentrifuges can be categorized into preparative ultracentrifuge and analytical ultracentrifuge. Preparative ultracentrifuges are used to separate the biological/organic components such as DNA, RNA, lipoproteins, membranes, organelles, and viruses. Analytical ultracentrifuges are used to identify samples in real-time. They can identify the equilibrium and velocity sedimentation, the shape and mass of molecules. Ultracentrifuges have a wide range of applications in the area of nanotechnology.

Centrifuge Applications

Centrifuges can be used for a wide range of applications in the laboratories. Some of the common applications for centrifuges are listed below:

• Separation of mixtures with close densities
• Immiscible liquids separation
• Separation of sediment suspended solids
• Extraction of blood cells
• Protein extraction
• Isotope separation
• Gravity simulation environments for astronauts
• Separating creams
• DNA extraction
• Plasmid DNA extraction (mainly bacteria or yeast)
• Material synthesis in a high gravity environment
• Washing machine spin function